linux-kernel - Re: [PATCH 5/7] signal: Add unsafe_copy_siginfo_to

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Date:   Tue, 15 Jun 2021 08:21:00 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-arch@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] signal: Add unsafe_copy_siginfo_to_user()

On Tue, Jun 15, 2021 at 09:03:42AM +0200, Christophe Leroy wrote:
> 
> 
> Le 15/06/2021 ?? 08:52, Christoph Hellwig a ??crit??:
> > On Tue, Jun 15, 2021 at 06:41:01AM +0000, Christophe Leroy wrote:
> > > +	unsafe_copy_to_user(__ucs_to, __ucs_from,			\
> > > +			    sizeof(struct kernel_siginfo), label);	\
> > > +	unsafe_clear_user(__ucs_expansion, SI_EXPANSION_SIZE, label);	\
> > > +} while (0)
> > 
> > unsafe_clear_user does not exist at this point, and even your later
> > patch only adds it for powerpc.
> > 
> 
> You missed below chunck I guess:
> 
> > diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
> > index c05e903cef02..37073caac474 100644
> > --- a/include/linux/uaccess.h
> > +++ b/include/linux/uaccess.h
> > @@ -398,6 +398,7 @@ long strnlen_user_nofault(const void __user *unsafe_addr, long count);
> >   #define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
> >   #define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
> >   #define unsafe_copy_from_user(d,s,l,e) unsafe_op_wrap(__copy_from_user(d,s,l),e)
> > +#define unsafe_clear_user(d, l, e) unsafe_op_wrap(__clear_user(d, l), e)

That doesn't help with architectures that define user_access_begin but
do not define unsafe_clear_user. (i.e. x86).